1. Field of the Invention
This invention relates to a tire capable of usually running even after being subjected to an external injury, and more particularly to a safety tire having excellent durability and ride comfort in the running after the tire is subjected to an external injury.
2. Description of Related Art
In a pneumatic tire, e.g. a pneumatic tire for a passenger car, air is sealed in an inside of the tire under an internal pressure of about 250-350 kPa (absolute pressure, and so forth) to generate tension in a skeleton portion of the tire such as carcass, belt and the like, and by this tension it is possible to conduct deformation and restoration of the tire due to input to it. That is, constant tension is generated in the skeleton of the tire by holding its internal pressure of the tire within a given range to provide a load bearing function and to enhance the rigidity for providing basic performances required in the running of a vehicle such as traction, braking, cornering performances and the like.
When the tire held at the given internal pressure is subjected to an external injury, air leaks out through the external injury toward an exterior to reduce the internal pressure up to an atmospheric pressure or render into so-called puncture state, so that tension generated in the skeleton portion of the tire is substantially lost. As a result, the load bearing function as well as the traction, braking and cornering performances obtained by applying the given internal pressure to the tire are also lost and hence it is impossible to run the vehicle provided with such a tire.
For this end, there are many proposals with respect to safety tires capable of running even at the puncture state. As a pneumatic safety tire for automobiles, there are proposed, for example, tires of various types such as a tire having a double wall structure, a tire including a load bearing device therein, a tire strengthening a sidewall portion and so on. As a practically used technique among these proposals, there is a tire wherein a sidewall reinforcing layer made of a relatively hard rubber is arranged in an inner face of the tire about a sidewall portion of the tire from a shoulder portion to a bead portion. This type of tire is used as so-called run-flat tire mainly having an aspect ratio of not more than 60%.
However, the method of adding the sidewall reinforcing layer increases a tire weight by 30-40% and raises a longitudinal spring constant of the tire, so that there is a disadvantage of bringing about a serious degradation of rolling resistance and a lowering of ride comfort in the usual running before puncture. Therefore, this method badly affects the performances in the usual running, fuel consumption and environment, and is a technique being still poor in the general-purpose property.
On the other hand, as a pneumatic tire having a high tire section height and an aspect ratio of not less than 60%, there is mainly adapted a run-flat tire having such a structure that an internal support body such as a core or the like is fixed to a rim to support a load in the puncture for avoiding heat build-up of the sidewall portion during the running at a relatively high speed over a long distance.
In this case, however, the tire can not withstand to local repetitive stresses produced between the tire and the internal support body at a run flat state after the puncture, and hence the running distance after the puncture is limited to about 100-200 km. In addition, there is a problem that an operation of arranging the internal support body inside the tire and assembling the tire onto a rim is complicated and requires a long time. In this connection, there is proposed means for forming a difference in a rim diameter between one end side and the other end side in a widthwise direction of the rim to facilitate the insertion of the internal support body, but a satisfactory effect is not yet obtained.
Moreover, in order to prolong the running distance after the puncture of the run-flat tire having the internal support body therein, it is effective to add a skeletal member to render the tire structure into a more massive state, but the rolling resistance and ride comfort in the usual running are degraded by the addition of the skeletal member, so that there is no reality in the adoption of this means.
Furthermore, a tire wherein a composite body having closed cells is filled in an inner space of an assembly of a tire and a rim is disclosed, for example, in JP-A-6-127207, JP-A-6-183226, JP-A-7-186610 and JP-A-8-332805. The tires proposed in these documents are mainly limited to a special or small-size tire such as agricultural tire, rally tire, motorcycle tire, bicycle tire or the like. Therefore, there is not known the application to tires regarding the rolling resistance and ride comfort as important such as tires for passenger car, tires for truck and bus and so on. And also, the composite body is low in the expansion rate, so that the weight of the composite body having the closed cells is large and it is unavoidable to degrade the ride comfort against vibration and fuel consumption. Furthermore, the inside of the closed cell is atmospheric pressure, so that the use of the composite body instead of a high pressure air in the conventional pneumatic tire is functionally insufficient.
In Japanese Patent No. 2987076 is disclosed a puncture-free tire inserting a foamed filling member into an inner peripheral portion of the tire. In addition to the disadvantage due to the fact that the internal pressure is very close to an atmospheric pressure, however, since the foamed body is urethane-base, energy loss resulted from intermolecular hydrogen bond of urethane group is large and self-heating is high. Therefore, when such a foamed body made of urethane is filled in the tire, heat generation is caused in the foamed body by repetitive deformation during the running of the tire to largely lower the durability. And also, since something that is hard to form closed cells is used as a starting material, the resulting cells are easily connected to each other and it is difficult to hold a gas in the foamed body, and hence there is a disadvantage that a desired internal pressure of the tire (load bearing ability or a deflection controlling ability) is not obtained.
Moreover, JP-A-48-47002 proposes a puncture-free tire wherein a plurality of expanded pressure cellular bodies each formed by integrally covering and sealing an outer periphery of a multi-cell body mainly composed of closed cells with an outer coating of rubber, synthetic resin or the like having a thickness of 0.5-3 mm are filled in an inside of a tire so as to hold a given internal pressure. According to this technique, in order to make a pressure in the cell of the cellular body higher than an atmospheric pressure, an amount of a foaming agent compounded in a starting material for the formation of closed cells constituting the expanded pressure cellular body is set to an amount generating gas in an amount at least equal to or more than an internal volume of the tire, whereby it is aimed at the development of performances at least equal to those of the usual pneumatic tire.
In the above technique, in order to prevent the scattering of gas in the cell of the expanded pressure cellular body, the body is integrally covered and sealed with the outer coating, but only materials such as tube for automobile or a blend for the formation of the tube are exemplified as a material for the outer coating. In other words, the multi-cell body is covered and sealed with a soft elastic outer coating mainly composed of butyl rubber having a low nitrogen gas permeability, which is used in a tire tube or the like, and a plurality of such covered multi-cell bodies are filled in the tire. As the production method, an uncured tire tube as the soft elastic outer coating and a starting material for the formation of an uncured cellular body as an expanded pressure cellular body are used and disposed in an inside of a tire-rim assembly and expanded by heating to obtain a tire filled with foamed bodies. By the expansion of the cellular bodies is naturally discharged atmospheric air inside the tire through a small hole opened in the rim.
Since the internal pressure of the tire for passenger car is generally set to about 250-350 kPa as an absolute pressure at room temperature, it is guessed from an equation of gas state that a pressure in the above tire filled with the foamed bodies is made to about 1.5 times of the above internal pressure at a heating state (about 140xc2x0 C.) for vulcanization and molding. However, such a pressure level brings about the lacking of vulcanization pressure and can not avoid to cause a blown. In order to avoid such a blown phenomenon, it is necessary that an amount of a foaming agent compounded is largely increased to raise a pressure generated by expansion or that a heating temperature is raised. However, in the method of increasing the amount of the foaming agent compounded, the internal pressure at room temperature largely exceeds 400 kPa by the increase of the foaming agent amount and hence it is difficult to use as a replacement of the conventional pneumatic tire. In the method of raising the heating temperature, the damage of the tire due to the heat aging becomes large and the durability of the tire is considerably degraded, so that there is caused a problem in the durability for use over a long time. On the other hand, many expanded pressure cellular bodies each covered with the soft elastic outer coating are disposed in the inside of the tire-rim assembly, so that a problem in view of the durability becomes large due to friction of the soft elastic outer coatings producing the above blown to each other, friction of the coating to the inner face of the tire and the inner face of the rim and the like. The above problems can be said to be large drawbacks resulted from the arrangement of many expanded pressure cellular bodies different from a case that a shape of the expanded pressure cellular body takes an integrally doughnut shape. And also, the small hole formed in the rim is effective to naturally discharge air of atmospheric pressure inside the tire due to the expansion of the expanded pressure cellular bodies, but serves as a scattering path of the gas in the cell of the expanded pressure cellular body and hence such a tire can not withstand for use over a long time.
Furthermore, the blend composition mainly composed of butyl rubber having a low nitrogen gas permeability for a tire tube or the like is used as the soft elastic outer coating, so that it is required to take a longer heating time for completing the vulcanization reaction at a temperature of about 140xc2x0 C. because the butyl rubber is very slow in the reaction rate. This means a lacking of crosslinking density in the soft elastic outer coating, which can be said to be a factor of generating the peeling of the soft elastic outer coating (will be mentioned in detail later). Moreover, the prolonging of the heating time can not be said to be a good plan because the damage of the tire due to the aforementioned heat aging becomes larger and the lowering of the durability can not be avoided.
It is, therefore, an object of the invention to provide a tire capable of stably running even after the tire is subjected to an injury without sacrificing the rolling resistance and ride comfort in the usual running.
It is another object of the invention to provide a composite body suitable as a filling material inside the tire and a foaming resin composition usable as a starting material thereof.
The inventor has made various studies in order to solve the above problems and found that it is effective to provide a structure that gas is not easily leaked out from an inside of the tire even when being subjected to an external injury or the like for always and properly holding an internal pressure of the tire.
Namely, the gist and construction of the invention are as follows.
(1) In a tire arranging a composite body consisting of a continuous phase made of a resin and many closed cells in an inside of a hollow doughnut-shaped tire, an improvement wherein the composite body has a cell content of 80.00 vol % to 98.75 vol % and an internal pressure at 25xc2x0 C. in the closed cell included therein is not less than 150 kPa as an absolute pressure.
(2) A tire according to the item (1), wherein the internal pressure at 25xc2x0 C. in the closed cell included therein is not less than 200 kPa as an absolute pressure.
(3) A tire according to the item (1) or (2), wherein the continuous phase of the composite body is made of at least one of resins having a polar functional group in their molecule and polyolefin resins.
(4) A tire according to the item (3), wherein the resin having a polar functional group in molecule is at least one of a polyvinyl alcohol resin, an acrylonitrile copolymer, an acrylic copolymer, a vinylidene chloride copolymer, an acrylonitrile/styrene resin, a polyester resin and a nylon resin.
(5) A tire according to the item (3), wherein the polyolefin resin is at least one of a polyethylene resin, a polypropylene resin and a polystyrene/polyethylene copolymer.
(6) A tire according to any one of the items (1) to (4), wherein the continuous phase of the composite body is made of a polyvinyl alcohol resin.
(7) A tire according to any one of the items (1) to (4), wherein the continuous phase of the composite body is made of an acrylonitrile polymer, and the acrylonitrile polymer is at least one selected from acrylonitrile polymer, acrylonitrile/methacrylonitrile copolymer, acrylonitrile/methyl methacrylate copolymer and acrylonitrile/methacrylonitrile/methyl methacrylate terpolymer and has a glass transition point of not lower than 80xc2x0 C.
(8) A tire according to any one of the items (1) to (4), wherein the continuous phase of the composite body is made of an acrylic polymer, and the acrylic polymer is at least one selected from methyl methacrylate resin, methyl methacrylate/acrylonitrile copolymer, methyl methacrylate/methacrylonitrile copolymer and methyl methacrylate/acrylonitrile/methacrylonitrile terpolymer.
(9) A tire according to any one of the items (1) to (4), wherein the continuous phase of the composite body is made of a vinylidene chloride polymer, and the vinylidene chloride polymer is at least one selected from vinylidene chloride/acrylonitrile copolymer, vinylidene chloride/methyl methacrylate copolymer, vinylidene chloride/methacrylonitrile copolymer, vinylidene chloride/acrylonitrile/methacrylonitrile copolymer, vinylidene chloride/acrylonitrile/methyl methacrylate copolymer, vinylidene chloride/methacrylonitrile/methyl methacrylate copolymer, vinylidene chloride/acrylonitrile/methacrylonitrile/methyl methacrylate copolymer and has a glass transition point of not lower than 80xc2x0 C.
(10) A tire according to any one of the items (1) to (4), wherein the continuous phase of the composite body is made of a nylon resin, and the nylon resin is at least one selected from nylon-6, nylon-11, nylon-12, nylon-6/66 copolymer and nylon-6/12 copolymer.
(11) A tire according to any one of the items (1) to (3), wherein the continuous phase of the composite body is made of at least one of a nylon resin, butyl rubber and a diene rubber.
(12) A tire according to any one of the items (1) to (11), wherein at least one gas selected from the group consisting of nitrogen, air, carbon dioxide, a linear or branched aliphatic hydrocarbon having a carbon number of 3 to 6, an alicyclic hydrocarbon having a carbon number of 3 to 6, and an aliphatic fluorocarbon or fluorohydrocarbon having a carbon number of 2 to 6 and containing no chlorine is included in the closed cells of the composite body.
(13) A tire according to the item (12), wherein a gas containing not more than 50% by weight of at least one selected from propane, normal butane, isobutane, pentane, isopentane and neopentane included in the aliphatic fluorocarbon or fluorohydrocarbon having a carbon number of 2 to 6 and containing no chlorine is included in the closed cells of the composite body.
(14) A tire according to any one of the items (1) to (13), wherein the continuous phase of the composite body has a gas permeability constant at 30xc2x0 C. of not more than 300xc3x9710xe2x88x9212 (cc. cm/cm2xc2x7sxc2x7cmHg).
(15) A tire according to any one of the items (1) to (13), wherein the continuous phase of the composite body has a gas permeability constant at 30xc2x0 C. of not more than 20xc3x9710xe2x88x9212 (ccxc2x7cm/cm2xc2x7sxc2x7cmHg).
(16) A tire according to any one of the items (1) to (13), wherein the continuous phase of the composite body has a gas permeability constant at 30xc2x0 C. of not more than 2xc3x9710xe2x88x9212 (ccxc2x7cm/cm2xc2x7sxc2x7cmHg).
(17) A tire according to any one of the items (1) to (16), wherein an innerliner layer is provided on an inner peripheral face of the tire and made of a thermoplastic elastomer composition containing nylon resin having a melting point of 170-230xc2x0 C. and a halide of isobutylene-paramethylstyrene copolymer in which an elastomer ingredient is dynamically cured to a gelation ratio of 50-95%.
(18) A tire according to the item (17), wherein the innerliner layer has a gas permeability constant at 30xc2x0 C. of not more than 20xc3x9710xe2x88x9212 (ccxc2x7cm/cm2xc2x7sxc2x7cmHg).
(19) A composite body comprising a continuous phase and many closed cells, in which the continuous phase is made of at least one of a polyvinyl alcohol resin, an acrylonitrile resin, an acrylic copolymer, a vinylidene chloride copolymer, an acrylonitrile/styrene resin, a polyethylene resin, a polypropylene resin, a polyester resin, a polystyrene/polyethylene copolymer and a nylon resin, and an internal pressure at 25xc2x0 C. in the closed cell is not less than 150 kPa as an absolute pressure.
(20) A composite body according to the item (19), wherein the internal pressure at 25xc2x0 C. in the closed cell is not less than 200 kPa as an absolute pressure.
(21) A composite body according to the item (19) or (20), wherein at least one gas selected from the group consisting of nitrogen, air, carbon dioxide, a linear or branched aliphatic hydrocarbon having a carbon number of 3 to 6, an alicyclic hydrocarbon having a carbon number of 3 to 6, and an aliphatic fluorocarbon or fluorohydrocarbon having a carbon number of 2 to 6 and containing no chlorine is included in the closed cell.
(22) A tire arranging a composite body consisting of a continuous phase made of a resin and many closed cells in an inside of a hollow doughnut-shaped tire, wherein the composite body is formed by expanding a foaming composition containing 1-50% by weight of a foaming agent as an average content.
(23) A tire according to the item (22), wherein the foaming composition is resin particles sealing the foaming agent therein.
(24) A tire according to the item (22) or (23), wherein the foaming agent sealed in the foaming composition is at least one of a thermal-decomposable foaming agent, a liquefied fluoride of ethane, a liquefied linear aliphatic hydrocarbon having a carbon number of 3 to 6 and a fluoride thereof, a liquefied branched aliphatic hydrocarbon having a carbon number of 3 to 6 and a fluoride thereof and a liquefied alicyclic hydrocarbon having a carbon number of 3 to 6 and a fluoride thereof.
(25) A tire according to the item (24), wherein the thermal-decomposable foaming agent is at least one selected from dinitrosopentamethylene tetramine, azodicarbon amide, paratoluene sulfonyl hydrazine and a derivative thereof and oxybisbenzenesulfonyl hydrazine.
(26) A tire according to any one of the items (22) to (25), wherein the composite body consists of a resin matrix and many closed cells.
(27) A tire according to any one of the items (22) to (26), wherein at least one gas selected from the group consisting of nitrogen, air, carbon dioxide, fluorocarbon of ethane, a linear aliphatic hydrocarbon having a carbon number of 3 to 6 or its fluorocarbon, a branched hydrocarbon having a carbon number of 3 to 6 or its fluorocarbon and an alicyclic hydrocarbon having a carbon number of 3 to 6 or its fluorocarbon is included in the closed cells of the composite body.
(28) A tire according to any one of the items (22) to (26), wherein at least one gas selected from the group consisting of nitrogen, air, carbon dioxide and an organic gas having a carbon number of 3.